1. Field of the Invention
The present invention relates to an apparatus and method for measuring the corrosion current induced by microbiological activities on a metal electrode using two galvanically coupled electrodes in dual cells which are electrolytically continuous, chemically continuous and biologically separated. The contributions of individual microbiological mechanisms can also be evaluated using the apparatus.
2. Description of the Prior Art
Over the last fifty years, microbiologists and corrosion engineers have been documenting the corrosive effects of microorganisms attached to metal surfaces in a variety of media. Despite this recognition and documentation, the quantification of the electrochemical impact of microorganisms and individual mechanisms for microbiologically induced corrosion has remained elusive because of the complexity of microbiological processes and lack of analytical techniques.
Attempts to measure microbiologically induced corrosion have been made using polarization techniques that are accurate only for general corrosion on homogeneous metal surfaces. Polarization techniques assume a metal is corroding by a Wagner-Traud mechanism, i.e., that anodic and cathodic processes occur with equal probability on all parts of the corroding metal surface. Metal surfaces colonized by microorganisms are not homogeneous and the resulting corrosion is localized, not general. Anodic and cathodic areas are distinct in space and stable in time. This invention allows a separation of anodic and cathodic areas.
Prior known corrosion measuring devices such as described in U.S. Pat. No. 3,605,151 to E. Schaschl et al and Japan Patent No. 59-48469 to Takashi Yamamoto have used techniques to separate anodic and cathodic areas to evaluate abiotic corrosion processes. However the prior art does not provide a means to maintain biological separation between the two electrodic areas. Neither apparatus biologically separates the electrolyte of the two cells, nor do they maintain a constant and measured flow of the electrolyte.